From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/mfd/act8945a.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 drivers/mfd/act8945a.c (limited to 'drivers/mfd/act8945a.c') diff --git a/drivers/mfd/act8945a.c b/drivers/mfd/act8945a.c new file mode 100644 index 000000000..cafefb445 --- /dev/null +++ b/drivers/mfd/act8945a.c @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * MFD driver for Active-semi ACT8945a PMIC + * + * Copyright (C) 2015 Atmel Corporation. + * + * Author: Wenyou Yang + */ + +#include +#include +#include +#include +#include + +static const struct mfd_cell act8945a_devs[] = { + { + .name = "act8945a-regulator", + }, + { + .name = "act8945a-charger", + .of_compatible = "active-semi,act8945a-charger", + }, +}; + +static const struct regmap_config act8945a_regmap_config = { + .reg_bits = 8, + .val_bits = 8, +}; + +static int act8945a_i2c_probe(struct i2c_client *i2c) +{ + int ret; + struct regmap *regmap; + + regmap = devm_regmap_init_i2c(i2c, &act8945a_regmap_config); + if (IS_ERR(regmap)) { + ret = PTR_ERR(regmap); + dev_err(&i2c->dev, "regmap init failed: %d\n", ret); + return ret; + } + + i2c_set_clientdata(i2c, regmap); + + ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_NONE, + act8945a_devs, ARRAY_SIZE(act8945a_devs), + NULL, 0, NULL); + if (ret) { + dev_err(&i2c->dev, "Failed to add sub devices\n"); + return ret; + } + + return 0; +} + +static const struct i2c_device_id act8945a_i2c_id[] = { + { "act8945a" }, + {} +}; +MODULE_DEVICE_TABLE(i2c, act8945a_i2c_id); + +static const struct of_device_id act8945a_of_match[] = { + { .compatible = "active-semi,act8945a", }, + {}, +}; +MODULE_DEVICE_TABLE(of, act8945a_of_match); + +static struct i2c_driver act8945a_i2c_driver = { + .driver = { + .name = "act8945a", + .of_match_table = act8945a_of_match, + }, + .probe = act8945a_i2c_probe, + .id_table = act8945a_i2c_id, +}; + +static int __init act8945a_i2c_init(void) +{ + return i2c_add_driver(&act8945a_i2c_driver); +} +subsys_initcall(act8945a_i2c_init); + +static void __exit act8945a_i2c_exit(void) +{ + i2c_del_driver(&act8945a_i2c_driver); +} +module_exit(act8945a_i2c_exit); + +MODULE_DESCRIPTION("ACT8945A PMIC multi-function driver"); +MODULE_AUTHOR("Wenyou Yang "); +MODULE_LICENSE("GPL"); -- cgit v1.3.1